Cathode sleeve



' A. J. VASSELLI CATHODE SLEEVE Nov. 25, 1941.

Filed March 30, 2 Sheets-Sheet 2 Y. RE

E Em m WJ T Y A N 0 m N A Patented Nov. 25, 1941 CATHODE SLEEVE Anthony J. ,Vasselli, Newark, N. J., assignor to Radio Corporation of America, a. corporation of Delaware Application March 30, 1940, Serial No. 326,863

5 Claims.

My invention relates to electron discharge devices, particularly to cathode sleeves of the indirectly heated type for such devices.

Cathode sleeves usually of nickel comprise either the drawn seamless tube or the seamed type tube made by rolling metal blanks into a cylinder and joining the edge, along the side of the cylinder. Neither type of sleeve has, all of the features, necessary for hi h strength and low cost. The seamed tubing, for example, has a rather bulky seam along one side and bows and buckles when heated and cooled over a wide range of temperatures, apparently because of the asymmetrical distribution of metal in the sleeve. Further, if the seamed sleeve is made with an integral connecting tab at one end, the blank must be cut with a considerable waste of material. The seamless tubing has the disadvantage that it cannot be made with an integral tab, and is difficult to emboss to form the beaded stops for holding the sleeve in its insulating spacers.

An object of my invention is acathode sleeve that is stiff and strong and can be made inexpensively.

Another and more specific" objectof my invention is a cathode sleeve that can be made with an integral connecting tab with a minimum wastage of material.

Still another object of my invention is a seamed cathode sleeve that is symmetrical in cross section and has raised stops on the side of the sleeve for holding the sleeve in its support.

The characteristicfeatures of my invention are defined in the appended claims and preferred embodiments of my improved cathode and means for making the cathode are described in the following specification and shown in the accompanying drawings in which Figure 1 shows an electron discharge device for 'my improved cathode, Figure 2 shows one embodiment of my improved cathode in sectioned perspective view, Figure 3 shows diagrammatically one series of dies that may be used in making my improved cathode, Figure 4 shows in perspective a strip of metal formed by the dies of Figure 3, Figure 5 shows an end section of another cathode partly assembled and embodying my invention, and Figure 6 is an end section of the completed cathode sleeve of Figure 5. a

My novel cathode sleeve is adapted for mcunting in the conventional electrode assembly, such as shown in Figure 1;, where in envelope I,.anode 2 and grid 3 are supported at their ends in parallel insulating spacers 4, such as, mica or ceramic discs. Cathode 5 is of the indirectly heated type and comprises an externally activated cylinderv or sleeve as showningreater detail in Figure 2. The cathode sleeve comprises two semi-cylindrical pieces of, metal 6 and "I joined along their longitudinal edges. The edge portions or flanges ,8 and I0 of semi-cylindrical piece 6 andthe edge portions 9 and II of piece I are formed outwardly from the, barrel, of the cathode as shown in Figure 3 and are fixedly joined together to form a rigid metal cylinder. The joined, edge portions of the cylinder are folded against the side of the cylinder and serve as reinforcing ridges along the two seams on opposite sides of they sleeve. The registering edge portions of the semi-cylindrical piecesmay be joined as bywelding, hereinafter more fully described, or by the conventional lock, seam.

According to one of the principal featuresof my invention, one of the seams is terminated short'oi the ends of the cylinder so that ends l2 of the flanges on the outer surface of the cylinder conveniently serve as stops for insulators 4. The diameters of the holes in spacers 4 may be equal to the outside diameter of the cathode cylinder so that when the cylinder is inserted in the hole the ends E2 of the .seam overlie the edge of the holes and prevent longitudinal movement of the cylinder through the holes. A cathode tab may be provided at the endof the sleeve out of alignment, with the seam andshoulder l2. Preferably the tab is diametrically opposite the shoulder l2, and the material of the seam on the opposite side of the cylinder may-conveniently be extended beyond. the end of the barrel portion of the sleeve to form a tab. My improved double seam cathode sleeve with integral tab and mica stops is conveniently made on automatic machines with simple reciprocating forming dies. The dies of one machine for shaping the two semi-cylindrical pieces from strip metal and for welding their edge portions is shown in Figure 3 where the ends of the sleeves and the sides of the various forming dies may be viewed; Two strips of metal [3 and I4 are fed from right to left over a stationary arbor l5. Two welding electrodes [6 and I1 first press the strips together between the first arbor I5 and a second arbor I500, drawing and stretching the strips around the arbors, and welding them together. As the material is indexed to the left each cylinder comes into registry with recessed forming dies l8 and 19, which support the cylinders as unwanted portions of the metal are cut away. .One cutting die is shown at 29. Each cylinder with its two welding seams is finally removed from the strip by shearing knives 2| and 22 tapered at their ends to incline the welding seams from their normal stand-up position. Each cylinder is finally carried between forming blocks 23 and 24 on mandrel 25 and the two seams pressed down. The forming surfaces of the blocks 23 and 24 or mandrel 25 must be longitudinally recessed to receive the three layers of metal along each seam. It is apparent that the metal in either seam can be pressed to the inside or to the outside of the cylinder. In the particular machine shown, mandrel 25 is provided with a recess diametrically opposite a recess in forming die 23.

The several stages of cylinder forming are shown in end view in Figure 3 and in Figure 4 a perspective is given the strips with the dies removed and with the stage of manufacture indicated in the two figures as a, b, c, d, e and f, to show the metal as it is successively formed, drawn, welded and cut. Metal strip i3 reeled from a spoolof this material is of a width equal to the finished length of the cathode cylinder, and strip I4 is of a width equal to the combined length of the cylinderand its integral tab 28. Rectangular sections are blanked out of strip 14 to leave tabs 26 with suflicient metal to form when folded a two layer tab onthe finished sleeve. Tabs 26 could be blanked out any place along the edge of the strip, if desired, to have a. tab on the cylinder displaced from the seams. Two tabs, also, could be blanked out for each cylinder. Between positions a and b the two strips are drawn together and welded and the tab at the end in the example shown is grooved along its center preparatory to folding. The double thickness of metal between the cylinders is blanked out between positions and d, the cut-outs 21 being on one side tangent to the barrel and on the other side coextensive with the side of tab 25, the depth of the out being equal to the distance desired between the end of the barrel and the end H! of seam 8, 9. Cut-outs 2! are removed by cutting die 20. In position the cylinder with its two welded seams is severed from the strip by knives 2| and 22.

It is desirable to increase the electrical resistance between the two strips [3 and I4 where they are pressed together by the welding electrodes, so that less welding current is necessary for the weld. Indentations or beads I3a may be pressed in strip [3 so that only the beads contact strip I4 when welding current starts. Pressure of the electrodes force the two strips together as the beads melt. Alternatively, two parallel ridges Ifia may be machined in the face of welding electrode 16 so that the welding current may be concentrated along two lines parallel to the cylinders.

There is a considerable-saving of material in cathodes made according to my invention compared to the conventional cathode sleeve which is wrapped on a mandrel and seamed along one side. A wrapped cathode with an integral tab requires a blank equal in width to the circumference of the cathode, and as long as the total length of the sleeve and its tab. All of the material of this strip between the end of the tab and the end of I the sleeve, except for the material in the tab,

must then be removed. This wastage of material the two semi-cylindrical pieces 6 and 1 of my sleeve may be joined by the conventional lock seam as shown in Figures 5 and 6. One flange on each piece is made with flaps such as 8a and Ha so that it may be folded over the registering flanges to clinch the two semi-cylindrical pieces together. This clinched standing stem may then be folded against the side of the cylinder and the material of the two seams pressed either to the inside or to the outside of the cylinder as in the sleeve of Figure 2. The seam on one side of the cylinder may be cut off short of the ends of the cylinder to provide mica stops and two of the four of the layers in the other seam continued beyond the end of the cylinder to make a tab. When the sheet metal stock for the sleeves is of sheet metal about .002 inch in thickness it has been found preferable to make the tab of two thicknesses of folded metal from one edge of one of the semi-cylindrical pieces, although one, three or four of the flanges of the seam could be extended for the tab.

The finished cathode constructed according to my invention comprises a sleeve with reinforcing seams along opposite sides. These seams materially strengthen the sleeve and prevent bowing or buckling when heated to high temperatures. The symmetry of the metal in the cylinder is believed to contribute to the strength of the sleeve. The integral tab at the end of the sleeve is two thicknesses of the metal stock and is strong enough for handling yet flexible enough for easy attachment to the lead-in conductor in the stem. The seam on the sleeve opposite the tab is terminated short of the ends of the cylinder and provides convenient stops for the spacers. My improved cathode is stiff, strong and inexpensive to manufacture. My cathode combines the advantages of sleeves with integral embossings and integral cathode tabs in a cathode that is simple and strong.

I claim:

1. A cathode sleeve for an electron discharge device with reinforcing longitudinal seams extending along opposite sides of the sleeve, said seams comprising overlapping and joined edge portions of the sleeve, the joined portions of the seams being pressed against the sides of said sleeve.

2. A cathode sleeve with a seam extending longitudinally along one side of the sleeve, said seam comprising overlapped and joined edge portions of the sleeve, said overlapped portions of the seam lying outside the surface of the sleeve and terminating at one end short of the end of the sleeve, and a tab connected to said one end of the sleeve out of alignment with the terminated end of said seam.

3. A cathode sleeve comprising two semi-cylindrical pieces of sheet metal, the longitudinal edge portions of said two pieces overlapping and being joined together to form a cylinder, the joined portion of one seam terminating short of the ends of the cylinder, the overlapping portions of the other seam extending beyond the end of the cylinder.

4. A cathode sleeve for an electron discharge device, said sleeve having two parallel reinforcing seams extending longitudinally along the sides of said sleeve, said seams each comprising overlapping flanges along the registering edge portions of the sleeve, a flap on one flange of each seam being folded over the edge of the registering flange of that seam to secure the flanges together, and the three thicknesses of the metal in each seam including the two flanges and the flap being pressed against the side of said sleeve.

5. A cathode sleeve for an electron discharge device, said sleeve being fabricated from semicylindrical pieces of sheet metal and having seams extending longitudinally along opposite sides of said sleeve, said seams each comprising registering flanges along the registering edge portions of the pieces, a flap on one flange of each seam being folded over the edge of the registering 10 

